1. Field of the Invention
The present invention relates to an image display apparatus for displaying an image using fluorescent light produced with an application of display-use laser light.
2. Description of the Background Art
A display apparatus for use in a vehicle displays information concerning the vehicle mainly to a driver on an analog instrument or a digital instrument. The on-board display apparatus uses a display method employing an analog-type pointer or indicator or a display method employing a digital-type LED or electron tube having a combination of segments and is arranged to reliably present in real time various kinds of vehicle-related information which vary from time to time.
The driver, on the other hand, is required to recognize a situation outside the vehicle during driving, read the information displayed on the on-board display apparatus and perform maneuvers, for instance, safely and quickly. For the foregoing requirements, it is preferable that the information necessary for the driver to recognize the situation outside the vehicle during driving be displayed on the on-board display apparatus within a range where the driver's eyesight moves. Therefore, a development of, for example, an image display apparatus capable of displaying a text or an image by projecting laser light on part of a transparent plate like a windshield of the vehicle is desired.
As one example of the foregoing image display apparatuses, an image display apparatus which displays information with regard to the vehicle being driven, navigational information, or the like on a windshield of the vehicle as a screen using laser light has been proposed. Specifically, for example, an information display area is provided on an inner surface of the windshield of a vehicle, and a display film, which is made of transparent resin containing fluorescent pigment and which gives off light of a desired wavelength is formed in the information display area. The information with regard to the vehicle is displayed on the display film using blue laser light incident thereon (to be referred to Japanese Unexamined Patent Publication No. 2000-168352, for example). With the display apparatus of the foregoing structure, the laser light is scanned over the display film while controlling amounts of transmitted light and reflected light to realize a display screen of improved definition and luminance, thereby realizing an image display apparatus which the driver can view information displayed thereon with ease.
Another example of the image display apparatus has been proposed wherein information is displayed on a translucent reflecting plate on the windshield of the vehicle, and a plurality of switches used in the vehicle are displayed on the translucent reflecting plate in such a manner that the driver of the vehicle can switch ON/OFF the switches as desired with a small number of eyesight movements and within a range of the eyesight movements (to be referred to Japanese Unexamined Patent Publication No. 1996-76050, for example). With this structure, the driver can promptly recognize the situation outside the vehicle or the information with regard to the vehicle, thereby permitting the driver to perform driving safely.
According to the foregoing conventional structures, however, with the sunlight which directly enters inside of the vehicle through the windshield lightens the vehicle interior, and therefore a difference in brightness between an image or the like displayed on a display screen and the vehicle interior becomes smaller, which makes it hard to see the displayed information. Furthermore, the information display area on the surface of the windshield is formed with the display film made of the transparent resin containing the fluorescent pigment. Therefore, ultraviolet rays contained in sunlight which directly enters the vehicle interior through the windshield may excite the fluorescent pigment within the transparent resin, which may cause such problem that a light may be emitted from an unintended area, thereby presenting a problem in that necessary information may not be displayed clearly.
Additionally, while the foregoing conventional structures utilize a laser source as a light source, the maintenance of safety has not been taken into consideration, in the point of preventing the driver's or passenger's eyes from having a laser beam entered therein resulting from the laser beam reflected or scattered from an non-intended or unexpected part.